The metallocene catalsts in combination with aluminium alkyls are scarcely active for the polymerization of olefins (U.S. Pat. No. 2,827,446). The controlled addition of small quantities of water to the polymerization medium remarkably increases the activity thus obtaining, sometimes, activities which are greatly higher than the ones obtained by using the known catalysts Ziegler-Natta (Makrom. Chem. 179, 2553 (1978) and 169, 163 (1973), DE 1022382, U.S. Pat. No. 3,184,416, U.S. Pat. No. 3,440,237). The controlled hydrolysis of alkyl aluminium leads to the obtainment of the corresponding aluminoxanes. When these aluminoxanes are used as activators of metallocene catalysts a very active catalytic system for the polymerization of olefins is obtained, particularly with zirconocene catalysts (U.S. Pat. No. 4,542,199).
On the other hand it was found out (EP 277004 and EP 426637) that the use of bulky boron compounds as co-catalysts enables high activities in the polymerization of xcex1-olefins too. The co-catalysts act by forming and stabilizing the active cations by means of non-coordinative anions, without preventing the incorporation of olefin during polymerization.
These catalytic systems are homogeneous catalysts soluble in the known solvents used in the polymerization of olefins and form very small polymer particles ( less than 100 xcexcm). Therefore, when these systems are used in gas phase or in suspension, a fouling or blocking of the reaction systems often takes place, thus forcing the stopping of the polymerization plant causing a loss in the production.
For these reasons, it is suitable to develop the heterogeneous catalysts which are able to keep the catalytic activity of the homogeneous systems and to control the dimensions and the morphology of the resulting polymer for the obtainment of particles greater than 100 xcexcm and a high density of particles in the reactor (apparent density).
Works concerning the development of these catalytic solids have been carried out for many years. In general, the more used methods consist in the heterogeneization of the co-catalyst, the heterogeneization of the metallocene compound or in the heterogeneization of both components on an appropriate support.
The patent WO 91/09882 discloses the preparation of a supported catalytic system useful for the polymerization of olefins in suspension or in gas phase, which is formed by a homogeneous metallocene compound and an ionic non-coordinative co-catalyst of boron supported on an inorganic porous oxide. The support and the co-catalyst are physically joined, this fact can cause the migration to the reaction medium of the co-catalyst, thus obtaining products with a low apparent density and with a wide distribution of particle sizes. Moreover, the catalytic activity is very small. In a later patent (WO 93/11172) a method of lieterogeneization of said type of co-catalysts consisting in the functionalization of the boron co-catalyst bv means of two methods is disclosed. In one of them, the functionalization takes place with groups able to react with the free hydroxyl-groups of an inorganic support and, in the other method, functional groups are introduced in order to enable the later polymerization of the boron compound, creating an insoluble polymer in the reaction medium. Even though the chenmical anchorage of the co-catalyst assures that the active centers do not migrate in the reaction medium, these methods are chemically and economically expensive.
The patent EP 293 815 discloses the heterogeneization of metallocene catalysts supported on the inorganic oxides by the chemical reaction betwveen the functional alcoxysilane groups of the organometallic compounds and the surface hydroxyl groups of the inorganic oxides. The activity in the polymerization is not very high, probably as a consequence of the possible deactivation of the metallocene for the secondary products, which are formed during the reaction with the support.
The patent DE 3 840 772 A1 discloses the preparation of metallocene catalysts supported by reaction, between poly(methylhydrogensiloxane) and functionalized metallocenes with vinylic groups in the presence of a platinum catalyst. The process of synthesis and further anchorage of this kind of metallocene compounds are economically very expensive and the purity degree of tlhe supported metallocene is not the desired one resulting in very low polymerization activities.
The patents U.S. Pat. No. 4,659,685, EP 318 048, U.S. Pat. No. 50,302,562, EP 260 130 and EP 447 070 disclose the preparation of heterogeneous catalysts by directy supporting a non-metallocene compound of the metals of the groups 4, 5, or 6 of the periodic table on magnesium chloride, silica or aluminium phosphate, generally titanium halides, and a metallocene compound. The catalytic system is activated by the subsequent addition of aluminoxane or its mixtures with alkyl aluminium. The different polymerization rate of the titanium halides and of the metallocene compounds form multimodal polyolefins, by preventing the obtainment of polymers with a narrow and controlled polydispersity.
The patent EP 474 391 A2 and the studies of K. Soga (Macromol. Chem. Rapid Commun. 12, 367 (1991)) and of S. Collins (Macromoleculas 25, 1780 (1992) disclose the preparation of heterogeneous metallocene catalysts by supporting them onto inorganic porous oxides, magnesium halides or their mnxtures, previously treated with organoaluiminium compounds. The thus obtained catalysts are used in the polymerization of olefins in gas phase or in suspension and are activated with organoaluminium compounds. The resulting activities are very low and the obtained copolymers do not show a random distribution of the comonomer, thus developing two melting peaks. On the other hand, the metallocene compound cannot remain perfectly anchored because a migration in the polymerization medium may occur, with the relative obtainment of small particles.
The patent EP 628 566 and K. Soga in a study published in Makrom. Chem. Phys. 195, 3347 (1994) disclose the direct synthesis of metallocene catalysts on an inorganic support. The method consists in the chemical reaction between alkaline cyclopentadienyl cations and the functional groups of the support, the subsequent reaction of the resulting solid with halides of transition metals of groups 4, 5, or 6, allows the formation xe2x80x9cin situxe2x80x9d of the metallocene onto the support. The resulting activities in polymterization are very low; this is probably due to the by-products of the synthesis reaction whose separation from the catalyst is difficult.
On the other hand, there are no clear evidences of the fact that for this process it is possible to synthesize directly and in a good yield, the organometallic complexes onto the supports.
The patents U.S. Pat. No. 5,057,475, EP 206 794 A1 and U.S. Pat. No. 4,701,432 A1 disclose a method for the preparation of supported metallocene aluminoxane catalytic systems, by means of the simultaneous or subsequent addition of a metallocene compound and an aluminoxane onto an appropriate support. These catalysts can be used in polymerizations with or without additional co-catalyst. But for some kind of uses, the produced polymers have molecular weights and incorporation of co-monomer below the desired level. Moreover, the absence of appropriate interactions between the catalytic components and the support could cause the migration of the organometallic compounds during polymerization.
The patents U.S. Pat. No. 4,939,217 and U.S. Pat. No. 5,064,797 disclose the preparation of a supported aluminoxane by means of bubbling of a moistened inert gas in a solution of alklyl aluminium in the presence of the support. When a solution of metallocene is added, a heterogeneous catalytic system with good activities in the polymerization of olefins is obtained. But the thus obtained aluminoxane particles could not remain completely anchored onto the inorganic support because neither the morphology, nor the distribution and the size of the particle are the desired ones for this kind of uses. Consequently the apparent density and homogenity of the polymer obtained by these heterogeneous catalysts is not the appropriate one. Moreover, for this method, the reproduction of the structure and of the molecular weight of the synthesized aluminoxane is very difficult, thus strongly jeopardizing the catalytic activity.
The patents EP 323 716, EP 361 866, EP 336 593, EP 367 503, EP 363 644 and U.S. Pat. No. 5,057,475 disclose the preparation of supported catalysts by means of the xe2x80x9cin situxe2x80x9d formation of aluminoxane onto silica by the reaction of aluminium alkyls with small quantities of water (6-50%) contained in the silica. Then, they impregnate the metallocene compound on the silica covered with aluminoxane. There are no data concerning the morphology and distribution of the particles sizes of the resulting polymer, but small particles of polymer are probably obtained since the metallocene is not strongly kept on the support, because it could migrate in the reaction medium.
The patent EP 314 797 discloses the preparation of catalytic systems supported by means of impregnation of the metallocene compound onto supports obtained by the precipitation of aluminoxane in an aliphatic solvent in which the aluminoxane is insoluble or by the co-precipitation with inert components such as polyethylene or inorganic solids totally or partially dehydroxylated. The thus formed catalyst is pre-polymerized by using organoaluminium compounds as co-catalysts. The polymerization activities are good but they do not supply data concerning the morphology and the distribution ot the particle sizes.
In the present invention a process for the obtainment of heterogeneous catalytic systems is described by using properly functionalized inorganic supports and metallocene catalysts. The use of these functionalized supports involves a strong anchorage between the catalytic support and the active species preventing their separation in the polymerization medium. The described method allows the obtainment of metallocene heterogeneous catalyst which properly control the morphology and the distribution of the particle sizes showing typical catalytic activities of the homogeneous catalysts.
In the present invention heterogeneous catalytic systems resulting from the mixture of two components A and B are described, which are able to polymerize and co-polymerize xcex1-olefins, especially to homopolymerize ethylene and co-polymerize ethylene with xcex1-olefins. The catalytic activities are similar to those of the homogeneous catalysts. The polymers obtained with this kind of catalytic systems are characterized in that they have narrow distribution of molecular weights show a good distribution of the particle sizes and they reproduce the morphology of the catalytic support. Moreover, these catalysts are particularly suitable in the incorporation of the co-monomcr, by forming copolymers with completely random co-monomer distributions.
Thus it is an object of the present invention to provide a catalyst component (A) for the polymerization of xcex1-olefins in suspension, in gas phase at low and high pressures and temperatures or in a mass at high pressures and high or low temperatures, comprising:
a) a functionalhzed support (A.1) result from the reaction of an inorganic porous support constituted by one or more oxides of the elements of groups 2, 13 or 14 of the periodic table, dehydrated or not and a functionalizing compound of general formula: 
wherein:
R1 is halogen, alkoxide of formula OR, R being a branched or a linear alkyl having from 1 to 6 carbon atoms, a C5-C7 cycloalkyl, a C6-C10 aryl, a C2-C10 alkenyl, a C7-C10 arylalkyl or a C7-C40 alkylaryl;
R2, R3, R4 and R5, equal to or different from each other, are linear or branched C1-C6 alkyl, C5-C7 cycloalkyl C6-C10 aryl, C2-C10 alkenyl, C7-C10 arylalkyl, or a C7-C40 alkylaryl;
R6 is a methylene or propylene group;
F is selected from the group consisting of: xe2x80x94NH2, xe2x80x94NHR, xe2x80x94SH, xe2x80x94OH, or xe2x80x94PHR wherein R has the above defined meaning;
the addition of a+b+c is equal to 3, a being always higher than 0;
d, e can have independently values between 0 and 10;
b) an organo aluminium compound (A.2)
c) one or more metallocene complexes of groups 3, 4, 5 and 6 of the periodic table (A.3) represented by the general formula III: 
wherein:
M is a transition metal of the groups 3, 4, 5 or 6 of the periodic table;
Each X is independently selected from the group consisting of hydrogen, halogen, linear or branched alkyl having from 1 to 10 carbon atoms, C1-C10 alkoxyl C5-C7 cycloalkyl, C6-C10 aryl, C6-C10 aryloxyl, C2-C10 alkenyl, C7-C10 arylalkyl, C7-C40 alkylaryl or C8-C40 arylalkenyl;
L1 is selected from the group consisting of: cyclopentadienyl (Cp) of formula: 
indenyl (Ind) of formula: 
fluorenyl (Flu) of formula: 
wherein W is independently selected from the group consisting of hydrogen, linear or branched alkyl groups from 1 to 10 carbon atoms, C5-C7 cycloalkyl which can be substituted by an alkyl having from 1 to 6 carbon atoms, C6-C10 aryl, C2-C10 alkenyl, C7-C10 arylalkyl or C7-C40 alkylaryl, a group of general formula (IV): 
wherein:
R7, R8, R9, R10, R11, R12, R13 and R14, equal or different from each other are hydrogen, linear or branched alkyl groups having from 1 to 10 carbon atoms, C5-C7 cycloalkyl, which can be substituted by an alkyl having from 1 to 6 carbon atoms, C6-C10 aryl, C2-C10 alkenyl, C7-C10 arylalkyl or C7-C40 alkylaryl, R7 and R8 can also be equal to Y;
Y can be a halogen (i.e. F, Cl, Br I) or NR11R12 or hydroxyl;
o, p, q, r, s are integers which can have values comprised between 0 and 10;
u=5-g;
v=7-g;
z=9-g;
D has the meaning of L1 or is an heteroatom belonging to 13, 14, 15, or 16 groups of the periodic table;
A is a group which binds the ligands L1 and D according to the formula (V): 
wherein T is carbon, silicon, germanium or tin; and R7 and R8 are those previously defined; j is an integer which can have the values of 0, 1, 2, 3 or 4; k is an integer which can have the values of 0, 1, 2 or 3;
n, m and h are integers so as their addition is equal to 4; m and n have the values of 0.1 or 2 so that their addition can be only 1 or 2; h can never be higher than 3; g is an integer comprised between 0 and 2; when h is equal to 3 then the sum of m+n is equal to 1 and g is 0.
Preferably the metallocene for the preparation of the supported catalyst A are represented by the following formula (IIIa): 
wherein
M is a transition metal of the groups 3, 4, 5 or 6 of the periodic table;
Each X is independently selected from the group consisting of hydrogen, halogen, linear or branched alkyls having from 1 to 10 carbon atoms, C1-C10 alkoxyl, C5-C7 cycloalkyl, C6-C10 aryl, C6-C10 aryloxyl, C2-C10 alkenyl, C7-C10 arylalkyl, C7-C40 alkylaryl or C8-C40 arylalkenyl;
L1, L2 are independently selected from the group consisting of: cyclopentadienyl (Cp) of formula: 
indenyl (Ind) of formula: 
or fluorenyl (Flu) of formula: 
wherein each W is independently selected from the group consisting of hydrogen, linear or branched alkyl group from 1 to 10 carbon atoms, C5-C7 cycloalkyl wlich can be substituded by an alkyl having from 1 to 6 carbon atoms, C6-C10 aryl C2-C10 alkenyl, C7-C10 arylalkyl or C7-C40 alkylaryl, a group of general formula (IV): 
wherein:
R7, R8, R9, R10, R11, R12, R13 and R14, equal to or different from each other are hydrogen, linear or branched alkyl groups having from 1 to 10 carbon atoms, C5-C7 cycloalkyl, wiich can be substituted by an alkyl having from 1 to 6 carbon atoms, C6-C10 aryl, C2-C10 alkenyl, C7-C10 arylalkyl or C7-C40 alkylaryl, R7 and R8 can also be equal to Y;
Y can be a halogen (F, Cl, Br I) or NR11R12 or hydroxyl;
o, p, q, r, s are integers which can have values comprised between 0 and 10;
u=5-g;
v=7-g;
z=9-g;
A is a group which binds the ligands L1 and L2 according to the formula (V): 
wherein T is carbon, silicon, germanium or tin; and R7 and R8 are those previously defined; j is an integer which can have the values of 0, 1, 2, 3 or 4; k is an integer which can have the values of 0, 1, 2 or 3;
m, n, and h are integers so as their addition is equal to 4; m and n have the values of 0, 1 or 2 so that their addition can be only 1 or 2; h can never be higher than 3; g is an integer comprised between 0 and 2; when h is equal to 3 then m+n are equal to 1 and g is 0.
In the metaflocene of formula (III) and (IIIa) M is preferably selected from the group consisting of Ti, Zr or Hf. This catalyst component can be used with a co-catalyst which is employed for the activation of the metallocene and it is constituted by non-coordinative ionising compounds; preferably said co-catalyst is selected from the group consisting of methylaluminoxane or boron bulky compounds.
The used catalytic support can be an inorganic compound having a spherical morphology and with superficial hydroxyl groups such as: oxides, silicates, carbonates phosphates, clay and their mixtures. Catalytic supports which are preferably used are silica, alone or in combination with oxides of aluminium, titanium, vanadium, chromium, phosphorous, aluminium and phosphorous or their mitures. The stuface area of these supports can vary between 10-1000 m2/g preferably between 150-650 m2/g, the pore volume can vary preferably between 0.2-4 cm3/g preferably between 0.6-2.7 cm3/g and the average particle size can vary between 1-500 xcexcm, preferably between 5-200 xcexcm.
Generally these inorganic supports have different contents of water which can be removed or not. Supports are preferably thermally treated in order to remove the water and reduce at will the concentration of the superficial hydroxyl groups. Said treatment is carried out in a fluidized bed by heating the support in the presence of a dry inert gas, at temperatules comprised between 100 and 1000xc2x0 C. and preferably between 200 and 800xc2x0 C. Once the drying process is completed, the support can be stored for a long time in the absence of air and humidity.
Once calcined the content of hydroxy groups on the surface of she support can be determined by means of a volumetric evaluation of the separated ethane by treating a suspension of the support with a volume of a solution of triethylaluminium in a hydrocarbon solvent. The surface concentration of hydroxyl group depends on the calcination temperature and can vary between 0.1 and 4 meq OH/g of support, preferably bet een 0.3-3 meq OH/g of support.
The functionalization of the catalytic support is carried out by reaction between the surface hydroxyl group of the inorganic support and the reactive groups R1, of the compound ol formula (I), in molar ratios OH/R1 comprised between 0.10 and 6, preferably between 0.2 and 4. The reaction is carried out in aliphatic or aromatic hydrocarbon solvents (toluene, heptane, etc.), by keeping the temperature of the reaction medium between 25xc2x0 C. and 150xc2x0 C., working preferably between 50 and 130xc2x0 C. and for 5-36 hours, preferably between 10-30 hours. The reaction by-products which are generally inert, can be easily removed by filtration and washing with hydrocarbon solvents. The resulting solids have the general formula (II): 
the functional groups will be more or less close to the surface of the support, depending on the value of d and e. The value of f depends on the concentration of hydroxyl groups on the surface of the support and on the molar ratios OH/R1 used in the silanization reaction.
The supported catalysts of the present invention are prepared by adding the organo aluminium compound to a suspension formed by the functionalized catalytic support and the solvent. Afterwards, on the resulting solid, a solution formed by one or more metallocene organometallic complexes of the elements of the groups 3, 4, 5 or 6 of the periodic table and a hydrocarbon solvent are added. It is desirable that the formed reaction byproducts be inert, volatile or easily extractable from the medium with the aim of avoiding that the catalytic system is contaminated; the catalytic activity could be jeopardized.
The quantity of the organoaluminium compound used can vary from 0.05 to 30 mmoles of Al/g of support, preferably the concentration will be in the range from 1 to 15 mmoles Al/g of support. The reaction is carried out during 1-24 hours, preferably between 2 and 15 hours, in a temperature range comprised between 15 and 200xc2x0 C., preferably between 20 and 150xc2x0 C. The solids obtained by this process show aluminium contents comprised between 2 and 20%, preferably between 5 and 15%. The quantity of metallocene added to the functionalized support covered with organoaluminiuim can vary between 0.01 and 10 mmoles of metal/g of support, preferably between 0.1 and 7 mmoles of metal/g of support. The reaction is carried out at temperatures comprised between 0 and 190xc2x0 C., preferably between 20 and 130xc2x0 C., during 1-20 hours, preferably between 2-15 hours. The content of the transition metal of the heterogeneous catalyst obtained depends on the content of aluminium of the support and can vary between 0.05 and 6%.
During the whole process both the chemical species and the solvents as well as the obtained products will be protected from oxygen and humidity. The heterogeneous catalysts will be stored in inert atmosphere, and will remain active in polymerization during long periods of time.
Further object of the present invention is a process for obtaining polyolefins characterized by the use of said catalytic system. The heterogeneous catalyst component (A), obtained according to the previous description, can be used in the polymerization or co-polymerization of xcex1-olefins by addition of the co-catalysts, component B. These co-catalysts are non-coordinative ionizing compounds such as alkyl aluminoxanes or bulky perfluoro boron compounds. Representative but not limitative examples are methylaluminoxane, dimethylanilinotetrakis (pentafluorophenyl) boron and trispentafluorophenylborane. If boron derivatives are used, it is advisable to add to the polymerization medium small quantities of alkylaluminium (TIBA, TEA, TMA, etc.).
The so prepared catalytic systems are suitable for the polymerization of xcex1-olefins lhaving from 2 to 20 carbon atoms, particularly for the polymerization of ethylene. and for the co-polymerization of ethylene with one or more xcex1-olefins having from 3 to 20 carbon atoms, such as propylene, 1-butene, 4-methylpentene, 1-hexene, etc. with dienes and cycloalkenes. The polymerization can be carried out by polymerization processes in suspension, in gas phase or in mass at high pressures and tempcratures. In suspension polymerization it is used as a reaction medium a hydrocarbon solvent such as linear or branched aliphatic hydrocarbons (hexane, heptane, isobutane, etc.), cyclic hydrocarbons benzene, toluene, xylene, etc.) or a mixture thereof are used. The polymerization can be carried out between 1 and 2000 atmospheres and temperatures generaly between xe2x88x9260xc2x0 C. and 280xc2x0 C., optionally between 60 and 240xc2x0 C., preferably between 40 and 180xc2x0 C. and the polymerization time can vary between 20 seconds and 6 hours depending oil the process.
The used concentration of the supported metallocene catalyst (component A), referred to the transition metal (M), ranges from 10xe2x88x927 to 10xe2x88x923, preferably from 10xe2x88x926 to 10xe2x88x924 moles of transition metal/l of solvent. The co-catalyst (component B) is used in a concentration from 10xe2x88x924 to 10xe2x88x921, preferably from 10xe2x88x923 to 10xe2x88x922 moles/l of solvent. Higher concentrations of both components are also possible. When aluminoxanes are used as co-catalysts the used molar ratio Al/M generally ranges from 10 to 10000, optionally from 100 to 10000, preferably between 500 and 1500. When boron compounds are used, the molar ratio B/M varies between 0.5 and 10, preferably between 0.9 and 5.
The preparation of the catalytic system for the polymerization of olefins can be carried out by mixing the components A and B in the polymerization reactor saturated with monomer or by mixing the components out of the reactor and adding the mixture to the reactor.
The molecular weight of the obtained polymer can be controlled varying the concentrations of the catalyst, of the co-catalyst and of the monomer in the polymerization mediumn as well as the polymerization temperature with the addition of molecular weight regulators such as H2. When in the preparation of the catalyst a single metallocene compound is used, polymers with narrow distributions of molecular weights ranging betveen Mw/Mn=2-4 are obtained. When two or more metallocene compounds are used, the obtained polymers have broader molecular weight distributions including multimodal distributions. Preferably, the polymer does not contain particles having size less than 100 xcexcm.
The co-polymerization reaction can be realized by using the same process as the one used in the processes of homopolymerization but feeding furthermore the reaction medium with the appropriate comonomer(s). The preferred molar ratios comonomer/monomer are comprised between 0.1 and 5. Copolymers are obtained with controlled contents of comonomer, random distribution and density ranging from 0.87 to 0.96 g/cc.
In order to better clarify the invention, some examples are described below. The materials, chemical compounds and conditions utilized in these examples are used in an illustrative way and not as a limitation of the claims of the invention. The average molecular weights by number, by weight and their distribution have been defined by GPC or SEC permeation gel chromatography. The thermal properties of the polymers have been defined by using differential scarnig calorimetry. The intrinsic viscosities [xcex7] have been obtained at 145xc2x0 C. by viscosinetric teclnique, the solvent used being trichlorobenzene with 0.05% antioxidant in order to avoid degradation. The determination of the particle sizes and of their distribution was carried out by laser technique. The mophology of said particles has been defined by optical and electronic microscopy.